CVE-2025-48700
📋 TL;DR
A Cross-Site Scripting (XSS) vulnerability in Zimbra Collaboration's Classic UI allows attackers to execute arbitrary JavaScript in users' sessions by sending specially crafted emails. This can lead to session hijacking, data theft, and unauthorized actions within the affected user's account. All Zimbra Collaboration users running versions 8.8.15, 9.0, 10.0, or 10.1 with Classic UI enabled are affected.
💻 Affected Systems
- Zimbra Collaboration (ZCS)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover, data exfiltration, lateral movement within the organization, and installation of persistent backdoors.
Likely Case
Session hijacking leading to unauthorized email access, contact list theft, and potential credential harvesting via phishing.
If Mitigated
Limited impact due to proper email filtering, user awareness, and security controls preventing malicious emails from reaching users.
🎯 Exploit Status
Exploitation requires sending crafted email to target user. No authentication needed to send email, but attacker needs target's email address.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Zimbra Security Advisories for specific patch versions
Vendor Advisory: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
Restart Required: Yes
Instructions:
1. Check Zimbra Security Advisories for patch details. 2. Apply the latest security patch for your version. 3. Restart Zimbra services. 4. Verify patch installation.
🔧 Temporary Workarounds
Disable Classic UI
linuxForce all users to use Modern UI (Ajax) which may not be vulnerable
zmprov mcf zimbraFeatureClassicEnabled FALSE
zmmailboxdctl restart
Enhanced Email Filtering
allImplement strict HTML/JavaScript filtering at email gateway
🧯 If You Can't Patch
- Implement strict Content Security Policy (CSP) headers to limit script execution
- Deploy web application firewall (WAF) with XSS protection rules
🔍 How to Verify
Check if Vulnerable:
Check Zimbra version and verify if Classic UI is enabled. Vulnerable if running affected versions with Classic UI active.Check Version:
su - zimbra -c 'zmcontrol -v'Verify Fix Applied:
Verify patch installation via version check and test with safe XSS payload in test email.📡 Detection & Monitoring
Log Indicators:
- Unusual email patterns with HTML/JavaScript content
- Multiple failed login attempts from same session
- Unexpected outbound connections from Zimbra server
Network Indicators:
- Suspicious email attachments with HTML content
- Unusual SMTP traffic patterns
SIEM Query:
source="zimbra.log" AND ("script" OR "javascript" OR "@import") AND "email_view"